The Sydney Metro is set to become three separate, incompatible lines

Sydney’s new driverless underground trains and stations may end up looking the same to commuters, but key differences in the mega-projects mean the city will build three lines, operated by three separate private operators, with trains not changing between them can.

Using different powertrains and trains built by different manufacturers, the new $11 billion subway line to Western Sydney Airport at Badgerys Creek will be incompatible with the first two legs of Sydney’s subway rail network.

The airport line will operate on 25-kilovolt AC when it opens in 2026, while the Metro Northwest and Metro City and Southwest lines will operate on 1500-volt DC.

Part of the 45-strong train fleet serving the Metro Northwest and City and Southwest lines.

Part of the 45-strong train fleet serving the Metro Northwest and City and Southwest lines. Credit: Nick Moir

As a result, the 12 autonomous trains that German company Siemens will build for the airport line will not be able to run on the Metro Northwest and the connecting City and Southwest lines. The airport line’s trains will be about 30 centimeters wider than other subways to accommodate passengers with luggage.

The different flow also means that the 45 driverless trains that French company Alstom has built in India for the city’s first two metro lines cannot be switched to the airport line. The $25 billion Metro West line — the largest of the four lines due to open in 2030 — will also not be able to operate because it too is powered by 25 kilovolts.

The airport line is designed for trains with up to four wagons, while trains with up to eight wagons are possible on the Northwest and City and Southwest lines.

Transportation and planning consultant Alex Gooding said it was highly unusual for subway lines in the same city to be deliberately planned so differently, such as the airport line, from both the Northwest, City and Southwest lines.

“We’re building a system from the ground up, but the previous government seemed to have intentionally built a bunch of incompatible features that don’t make sense,” he said.

Gooding said a likely reason for the difference is that building the airport line to accommodate the larger passenger capacity of the first two subway lines would have significantly increased their cost while also maintaining a “monopoly by a single private operator” in Sydney would have avoided.

“Instead of one subway, we will end up with three different and to varying degrees incompatible systems,” he said.

“Subways in overseas cities tend to have different lines, but are built with the same track systems and trains whenever possible.”

main differences

Metro Northwest/City and Southwest

  • Power supply: 1500V DC
  • Cars per train: six, with the possibility of increasing to eight
  • Train builder: French company Alstom
  • Operator: Metro Trains Sydney consisting of MTR, John Holland and UGL Rail

Metro Western Sydney Airport

  • Power supply: 25 kV AC
  • Cars per train: three, expandable to four
  • Train builder: German company Siemens
  • Operator: Parklife Metro consisting of Siemens, Plenary, Webuild and RAPT Dev

Metro West

  • Power supply: 25 kV AC
  • Further details are yet to be decided as contracts have yet to be awarded

When the main section of the City and Southwest lines opens next year, it will be operated by a private consortium led by Hong Kong’s MTR Corporation, which operates Metro Northwest.

In contrast, a separate consortium including Siemens, Australian infrastructure investor Plenary and Italian company Webuild will build and operate the airport line.

Gooding said the decision to electrify the Metro West line between Sydney CBD and Parramatta to 25 kilovolts and set up a dedicated facility to manage that project would likely result in there being a different operator from the other lines.

The new Labor government last month announced a major overhaul of the Metro West line as part of a wide-ranging review of Sydney’s underground projects.

Transport Secretary Jo Haylen said the integration of Sydney’s subway lines with each other and with the wider transport network is important and is the reason the Minns Government has commissioned a review of the projects.

“It is important to ensure that these projects are implemented in a way that is beneficial to passengers and that the metro services are properly embedded in the overall transport network,” she said.


Sydney Metro said each line is designed to operate independently to ensure the highest level of reliability with train configurations to suit the line’s customer requirements. “Sydney Metro has a responsibility to source rolling stock responsibly and to achieve optimal price and safety results for the benefit of taxpayers,” it said.

The agency said it conducted competitive bidding processes for each project to achieve the best outcome for taxpayers, which bolstered the resilience of the broader transport network and ensured passengers had access to the latest train technologies and systems.

The design of the Metro Northwest, City and Southwest lines was also influenced by the need to rebuild existing sections of line, such as the Epping-Chatswood railway, which, like the existing suburban rail network, operated on 1500 volt electricity.


Martin Locke, associate professor at the University of Sydney’s Institute for Transport and Logistics Studies, said one of the reasons behind the decision for various train builders and consortia was to boost competition in the bidding process for the projects.

“The importance of self-contained subway lines has outweighed the perceived benefits of interoperability. It was designed to provide resilience and avoid the issues Sydney Trains has experienced due to timetable disruptions and a system that has proven very vulnerable,” he said.

The rail lines that make up Sydney’s existing suburban rail system are intertwined, which has often led to major incidents on one route, causing significant delays to train services across the network.

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Justin Scaccy

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